A FOUP opener is adapted to open a FOUP door for establishing communication between a first controlled space within a FOUP and a second controlled space within a processing apparatus without involvement of exposure of workpieces (semiconductor substrates, glass substrates, etc.) contained in the FOUP to the atmosphere of an external contaminated space in the course of transfer of the workpieces. Thus, a port door belonging to the FOUP opener is provided with positioning pins (also called alignment pins) in accordance with the SEMI standard, for the purpose of establishing accurate positional alignment between the port door and the FOUP door. The positioning pins are attached to the port door in such a manner as to project from the outer surface of the port door. When the FOUP (Front-Opening Unified Pod) is placed on a placement table of the FOUP opener, and then the placement table advances, the positioning pins are inserted into respective pin bores provided in the FOUP door. Through insertion of the positioning pins of the port door into the pin bores of the FOUP door, the FOUP door and the port door are aligned with each other at a preset position.
However, the FOUP may be deformed in the course of repeated use of the FOUP, or pin bores of the FOUP from a certain maker may have positional errors that have arisen in the course of manufacture. As a result, the pin bores may slightly deviate from required positions. Since conventional positioning pins are attached perpendicularly and fixedly to the port door, a positional misalignment between the positioning pins of the port door and the pin bores of the FOUP door causes collision of the positioning pins with the FOUP door. Consequently, the port door and the FOUP door fail to be properly aligned with each other, resulting in a failure to open and close the FOUP.
In order to avoid the above-mentioned problem, an invention described in Japanese Patent Application Laid-Open (kokai) No. 2002-68362 has been conceived. According to the invention, positional correction is carried out as follows: when a positional misalignment arises between the positioning pins and the pin bores, tapers provided at distal ends of the positioning pins guide the positioning pins into the respective pin bores, whereby the entire port door having a floating structure is positioned in alignment with the FOUP door. In order to impart a floating structure to the port door, needless to say, a floating structure must be imparted to all of related components, such as latch keys and suction piping for providing a vacuum for vacuum-chucking the FOUP door. Thus, a very complicated structure results. Also, a large number of components are required. This is accompanied by deterioration in maintainability and increase in manufacturing cost. Further, according to the invention, the positioning pins advance and retreat while being subjected to a radial force; thus, particles are generated through mutual rubbing of components.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2002-68362